Sarra Boudaoud2021-03-292021-03-292021http://dspace.univ-msila.dz:8080//xmlui/handle/123456789/24090In this thesis, we study the notion of fuzzy pseudo ordered sets and some of its interesting properties, and then we introduce the concept of fuzzy trellis as a natural generalization of the trellis introduced by Skala with respect to a fuzzy pseudo order relation. In addition, we introduce the notion of fuzzy ideal (resp. fuzzy filter) as fuzzy sets on a crisp trellis and we present interesting characterizations of these notions. We pay particular attention to the principal fuzzy ideals (resp. filters) on a given trellis, which is more complicated than the same notions on a lattice. At the end, we provide various characterizations of intuitionistic fuzzy ideals (resp. fuzzy filters) on a latticePseudo order relation, Pseudo ordered set, Trellis, Lattice, Principal ideal, Principal filter, Fuzzy set , Intuitionistic fuzzy set.Thesis